1. Field of the Invention
The present invention relates to an inductor and a method for manufacturing thereof. More particularly, the present invention relates to an inductor having external electrodes disposed at a certain position on a molded magnetic material member so as to be electrically connected to inner electrodes embedded within a molded magnetic material member.
2. Description of the Related Art
As shown in FIG. 12, a surface mounting type inductor includes a coil (an inner conductor) 52 that functions as an inductance element embedded in a resin based magnetic material 51 made by blending a magnetic powder and a resin to produce a molded magnetic material member 53 having at two terminal surfaces, terminals 52a and 52b of the coil 52 which are exposed, and a pair of external electrodes 54a and 54b are arranged to be electrically connected to the terminals 52a and 52b of the coil 52.
This inductor may be manufactured by providing the external electrodes 54a and 54b on the molded magnetic material member 53 made by molding the resin based magnetic material 51 produced by blending a magnetic power and a resin. This inductor requires no firing process at a high temperature as has been required in ceramic inductors using conventional magnetic ceramics, thus facilitating the manufacture of the inductor.
The inductor using the resin based magnetic material as described above is manufactured, for example, by the following steps.
(1) Preparing a ferrite powder (a magnetic powder), ferrite-resin pellets (a magnetic material) prepared by kneading the ferrite powder with a resin, and a coil (an inner conductor) produced by molding a copper wire (an AIW wire) coated with an insulating resin (a polyamide-imide resin) into a coil.
(2) Then, a ferrite-resin molded body (a molded magnetic material member) 53 is formed, wherein the coil (the inner conductor) 52 that functions as an inductor element is embedded within the magnetic material 51 as shown in FIG. 6 by injection molding of the ferrite containing resin around the coil after allowing the ferrite-resin pellets to melt by heating.
(3) Subsequently, sand-blasting is performed on the area (the both terminal surfaces of the molded magnetic material member 53) on which external electrodes 54a and 54b (see FIG. 12) are to be provided on the surface of the molded magnetic material member 53 as shown in FIG. 7 to expose both terminals 52a and 52b (see FIG. 12) of the coil 52 from the molded magnetic material member 53, and removing an insulating coating film (a polyamide imide resin) on the coil 52.
(4) Subsequently, a Ni electroless plating is applied after applying a nucleation treatment for the electroless plating on the molded magnetic material member 53, and a Ni electroless plating film 55 is formed on the entire surface of the molded magnetic material member 53 as shown in FIG. 8.
(5) In the next step, a resist agent 56 is coated on the area as shown in FIG. 9 where the external electrodes 54a and 54b (see FIG. 12) are to be provided on the molded magnetic material member 53, the entire surface of which is covered with the Ni electroless plating film, and the resist film is dried.
(6) Then, the Ni electroless plating film 55 at the unnecessary portion on the surface of the molded magnetic material member 53 is removed by etching with an acid as shown in FIG. 10.
(7) Subsequently, the resist agent 56 is removed with an alkali (FIG. 11).
(8) Then, a Ni electroplating film 57 is formed on the Ni electroless plating film 55 as shown in FIG. 12 by applying a Ni electroplating on the molded magnetic material member 53. Finally, a Sn electroplating film 58 is further formed on the plating films 55 to form the three layered external electrodes 54a and 54b including the Ni electroless plating film 55, the Ni electroplating film 57, and the Sn electroplating film 58.
In the process for manufacturing the inductor using the foregoing resin-based magnetic material, the Ni electroless plating film 55 is provided on the entire surface of the molded magnetic material member 53, and the resist agent 56 is coated on the area where the external electrodes 54a and 54b (FIG. 12) are to be provided, followed by removing the resist agent 56 with an alkali after removing the unnecessary Ni electroless plating film 55 by etching with an acid. Consequently, the manufacturing process involves many steps thus complicating the process, as well as increasing the manufacturing costs. Moreover, the process requires a lot of labor to process unnecessary products generated in the etching step using an acid for removing the unnecessary portion of the Ni electroless plating film, and the step for removing the resist agent using an alkali.
To overcome the above-described problems, preferred embodiments of the present invention provide a method for efficiently manufacturing an inductor using a resin-based magnetic material, and further provide a reliable inductor at greatly reduced costs.
A first preferred embodiment of the present invention provides a method for manufacturing an inductor including the steps of molding a magnetic material prepared by blending a magnetic powder with a resin into a molded body having a desired shape so that an inner conductor that functions as an inductance element is embedded within the molded body, thereby forming a molded magnetic material member having a portion of the inner conductor exposed on a surface thereof, forming a selectively coated molded body (a molded body having a main portion that is selectively coated with an insulating resin) so that the areas on the surface of the molded magnetic material member except for the area to be provided with external electrodes is coated with the insulating resin, and forming the external electrodes including an electroless plating film on the area to be provided with the external electrodes (the area where the insulating resin is not coated) by applying electroless plating on the selectively coated molded body such that the external electrodes are electrically connected to the inner conductor.
In the method for manufacturing the inductor described above, after forming the molded magnetic material member, having the portion of the inner conductor exposed at a surface thereof, by using a resin based magnetic material, the selectively coated molded body is formed so that the area not provided with the external electrodes on the surface of the molded magnetic material member is covered with the insulating resin. The external electrodes are formed at desired areas by applying electroless plating film on the molded magnetic material member (the selectively coated molded body).
Consequently, a resist agent used in conventional manufacturing methods is not required in the present invention. As a result, the steps for removing the resist agent with an alkali or a solvent (simply referred as a liquid chemical hereinafter) and the steps for removing the electroless plating films by etching with acid are eliminated. Therefore, the manufacturing process of preferred embodiments of the present invention is greatly simplified and greatly reduces the manufacturing costs and the labor involved in manufacturing.
A second preferred embodiment of the present invention provides a method for manufacturing an inductor including the steps of molding a magnetic material prepared by blending a magnetic powder, a resin and a component functioning as nuclei for applying electroless plating into a molded body having a prescribed shape so that an inner conductor that functions as an inductance element is embedded within the molded body, thereby forming a molded magnetic material member having a portion of the inner conductor exposed on a surface thereof, forming a selectively coated molded body so that the area on the surface of the molded magnetic material member except for the area to be provided with external electrodes is coated with an insulating resin, and forming the external electrodes including an electroless plating film on the area to be provided with the external electrodes by applying electroless plating on the selectively coated molded body.
Since the resin based magnetic material prepared by blending a component that functions as nuclei for applying electroless plating is used in the method for manufacturing the inductor described above, electroless plating may be more efficiently applied on the surface of the molded magnetic material member than using a magnetic material prepared by merely blending a magnetic material with a resin.
The same advantages as the first preferred embodiment of the present invention are achieved in the second preferred embodiment of the present invention.
Preferably, the external electrodes are formed by applying electroless plating after roughening the area to be provided with the external electrodes on the molded magnetic material member by a blast medium blow method.
When electroless plating is applied after roughening the areas to be provided with the external electrodes on the surface of the molded magnetic material member by a blast medium blowing method (powder granules), an electroless plating film with a greatly improved adhesive property is formed on the surface of the molded magnetic material member. The blast medium blowing method is performed because the surface of the molded magnetic material member tends to provide insufficient adhesive strength with the electroless plating film.
The blast medium method (powder granules) for roughening the surface includes, for example, a dry blast method (a sand blast method) in which the surface of the molded magnetic material member is roughened by blowing a blast medium such as alumina powder and silica powder together with air, and a wet blast method in which the surface of the molded magnetic material member is roughened by spraying a blast medium such as alumina powder and silica powder together with a liquid, such as water.
The step for roughening the surface by the blast medium blowing method may be preformed before or after the step for coating the area not provided with the external electrodes with an insulating resin.
A third preferred embodiment of the present invention provides a method for manufacturing an inductor including the steps of molding a magnetic material prepared by blending a magnetic powder with a resin into a molded body having desired shape so that an inner conductor that functions as an inductance element is embedded within the molded body, thereby forming a molded magnetic material member having a portion of the inner conductor exposed on a surface thereof, coating the entire surface of the molded magnetic material member with an insulating resin, eliminating the insulating resin coating the area to be provided with the external electrodes on the surface of the molded magnetic material member by a blast medium blowing method, followed by roughening the exposed surface of the molded magnetic material member, and forming the external electrodes made of an electroless plating film on the area to be provided with the external electrodes by applying electroless plating on the molded magnetic material member.
The entire surface of the molded magnetic material member prepared by molding the resin based magnetic material is coated with the insulating resin, and the insulating resin on the area to be provided with the external electrodes is eliminated by a blast medium blowing method such as a sand blast method. The external electrodes made by the electroless plating films are formed on the area which is not coated with the insulating resin, by applying electroless plating on the molded magnetic material member after roughening the exposed surface on the molded magnetic material member.
Consequently, a resist agent that is required in the conventional manufacturing methods is not required in preferred embodiments of the present invention, and the steps for removing the resist agent with a liquid chemical, and the steps for removing the electroless plating films by etching with an acid are also eliminated. Accordingly, the manufacturing process is greatly simplified to greatly reduce the manufacturing costs and the labor required.
A fourth preferred embodiment of the present invention provides a method for manufacturing an inductor including the steps of molding a magnetic material prepared by blending a magnetic powder, a resin and a component that functions as nuclei for applying electroless plating into a molded body having a prescribed shape such that an inner conductor that functions as an inductance element is embedded within the molded body, thereby forming a molded magnetic material member having a portion of the inner conductor exposed on a surface thereof, coating the entire surface of the molded magnetic material member with an insulating resin, removing the insulating resin coating the area to be provided with the external electrodes on the surface of the molded magnetic material member by a blast medium blowing method, followed by roughening the exposed surface of the molded magnetic material member, and forming the external electrodes including an electroless plating film on the area to be provided with the external electrodes by applying electroless plating on the molded magnetic material member.
Since the resin based magnetic material member prepared by blending a component that functions as nuclei for applying electroless plating is used in the method for manufacturing the inductor described above, electroless plating is more efficiently applied on the surface of the molded magnetic material member than using a magnetic material prepared by merely blending a magnetic material with a resin.
The same advantages of the third preferred embodiment of the present invention are achieved in the fourth preferred embodiment of the present invention.
The external electrodes including an electroless plating film are provided on both end surfaces of the molded magnetic material member and on the portions extending from the both end surfaces to the outer circumferential surface thereof by applying electroless plating, after eliminating the insulating resin and roughening the exposed surface of the molded magnetic material member on both end surfaces of the molded magnetic material member and on the portions extending from the both end surfaces to the outer circumference surface thereof by the blast medium blowing method.
When the external electrodes are provided on both end surfaces of the molded magnetic material member and on the portions extending from the both end surfaces to the outer circumference surfaces by applying electroless plating, after roughening the both end surfaces of the molded magnetic material member and the portions extending from the both end surfaces to the outer circumference surfaces, inductors which are suitable for surface mounting and which have highly reliable electrical connections are efficiently manufactured when the inductors are mounted by, for example, a reflow soldering method or other suitable method.
Pd may be used for the component to function as nuclei for applying electroless plating.
When Pd is blended with the resin based magnetic material member as a component that functions as nuclei in applying electroless plating, an electroless plating film having outstanding adhesive strength is produced on the surface of the magnetic material member.
Preferably, the electroless plating films include a plurality of layers formed by applying different types of electroless plating in a plurality of steps.
Since the electroless plating includes a plurality of layers formed by applying different types of electroless plating in a plurality of steps in preferred embodiments of the present invention, electrodes having desired characteristics are provided.
Preferably, the method of manufacturing the inductor further includes a step of forming an external electrode including an upper electrolytic plating film with a monolayer or multilayer structure by additionally applying one or more types of electrolytic plating on the external electrodes including the electroless plating films.
Applying one or more types of electrolytic plating on the external electrode including the electroless plating film produces an external electrode having an upper layer electrolytic plating film on the electroless plating film, thereby providing an inductor having external electrodes with greatly improved reliability in electrical connection and soldering properties.
A fifth preferred embodiment of the present invention provides an inductor including an inner conductor that functions as an inductance element embedded within a molded magnetic material member made by molding a magnetic material prepared by blending a magnetic powder with a resin, and external electrodes with a monolayer or multilayer structure including at least electroless plating film layers formed on a roughened area on the surface of the molded magnetic material member, wherein the area not provided with the external electrodes on the surface of the molded magnetic material member is coated with an insulating resin.
The inductor described above has outstanding adhesive properties and a highly reliable electrical connection because the external electrode is formed on the roughened area on the surface of the molded magnetic material member formed by molding the resin type magnetic material. The inductor according to preferred embodiments of the present invention is efficiently manufactured by applying the aspects and other features of the present invention.
A sixth preferred embodiment of the present invention provides an inductor including an inner conductor that functions as an inductor element embedded within a molded magnetic material member formed by molding a magnetic material prepared by blending a magnetic powder, a resin and a component that functions as nuclei for applying electroless plating, and external electrodes with a monolayer or multilayer structure including at least one electroless plating layer formed on a roughened area on the surface of the molded magnetic material member, wherein the area not provided with the external electrodes on the surface of the molded magnetic material member is coated with an insulating resin.
Since the external electrodes are formed on the roughened area on the surface of the molded magnetic material member, the inductor has outstanding adhesive properties on the surface of the molded magnetic material member and a highly reliable electrical connection. The inductor is also efficiently manufactured by applying these and other aspects according to preferred embodiments of the present invention.
Other features, characteristics, elements and advantages of the present invention will become apparent from the following description of preferred embodiments thereof with reference to the attached drawings.